Power Allocation Algorithm Based On Cooperative Communication

With the further improvement of people's demand for wireless communication bandwidth,coverage and transmission capacity,people expect wireless communication network with more reliable quality of service(Qo S)and higher data transmission rate.However,in the communication process,multipath fading and noise affect the communication quality.In order to improve the quality of communication service,cooperative communication is introduced,which is an important part of modern communication technology.The core idea of cooperative communication is that multiple nodes in wireless network,such as relay and user terminal,cooperate with each other and use wireless channel,wireless network,physical layer transmission technology to design and optimize,so as to improve system performance.The most typical cooperative communication model is the three node cooperative communication model.The transmission process is that the source node first transmits the information to the relay node and the destination node,and then the relay node forwards the received information to the destination node,and obtains the corresponding diversity gain.In the process of cooperative communication,the relay node can complete information transmission,expand the coverage of the signal,avoid blind area and weak area,increase the channel capacity and improve the utilization of cell edge spectrum.In the process of cooperative communication transmission,all nodes participating in information transmission should not only transmit their own information,but also cooperate with other nodes to complete information transmission.The cooperation between nodes can ensure that mobile clients can obtain higher diversity gain.Therefore,it is very necessary to study the cooperative communication.In this dissertation,the quality of service and transmission rate of cooperative communication system are deeply studied in the single relay cooperative scenario,and a power allocation algorithm aiming at maximizing the information transmission rate of the destination node is proposed.The advantages of this algorithm are illustrated by simulation and comparison.The paper mainly includes three aspects:(1)This dissertation introduces the basic concept of cooperative communication,also introduces the transmission characteristics of wireless network channel: fast fading,slow fading and path loss;Amplify forward(AF)protocol,decode forward(DF)protocol and code Cooperation(CC)protocol.This paper introduces three performance indexes: channel capacity,outage probability and average error probability,and takes them as the standard of transmission performance;Several common cooperative communication network models and typical power allocation algorithms are introduced.This part of the basic knowledge laid the foundation for the next work.(2)Aiming at the single relay cooperative scenario,a power allocation scheme is proposed to maximize the information transmission rate of the destination node.The implementation process of the scheme is: under the premise of constraining the total transmit power of the node,the information transmission rate function of the destination node is constructed.The objective function is a convex optimization function,which is solved by Lagrange formula.When the information transmission rate of the destination node is the maximum,the transmission power of the source node and the relay node is the optimal value.This scheme aims to improve the system performance by optimizing the power allocation method of transmission nodes.In addition,the channel capacity of AF and DF single relay and multi relay systems is analyzed.(3)The simulation experiment studies the influence of the link distance between the source node and the destination node,the transmission power of the node,the signal-to-noise ratio and the position of the relay node on the information transmission rate.The results show that the node power increases with the increase of the distance between the source node and the destination node.Compared with other schemes,the proposed power allocation scheme has better performance and saves system resources.In addition,compared with non cooperative system,simulation results show that the channel capacity of cooperative communication is better,and the channel capacity obtained by DF is higher than that of AF mode.It shows that the AF mode also amplifies noise when amplifying the signal,so the performance of DF mode is better.